1. Field of Invention
The invention relates to Earth drilling and more particularly to structures associated with preventing items from falling down a hole at least partially occupied by the drilling shaft.
2. Description of Related Art
U.S. Pat. No. 6,584,734 disclosed a LOCKING GROUND HOLE COVER.
The locking ground hole cover that is disclosed comprises a cover plate with a scissor-type apparatus suspended therefrom which apparatus can be actuated from above the cover plate. The apparatus allows for the locking of a hole by pulling the cover plate down into a sealed locked position with the hole mouth. Variations on the device are disclosed in the '734 patent.